MANY PLANETARY SURFACE PROCESSES (LIKE PHYSICAL CHEMICAL AND ENERGETIC PARTICLE (SPACE) WEATHERING WATER ACTIVITY DIAGENESIS LOWTEMPERATURE OR IMPACT METAMORPHISM AND BIOGENIC ACTIVITY) LEAVE TRACES OF THEIR ACTIONS AS FEATURES IN THE SIZE RANGE 10S TO 100S OF MICRONS. THE MAPPING X-RAY FLUORESCENCE SPECTROMETER ( MAPX ) IS INTENDED TO PROVIDE ELEMENTAL IMAGING AT =100 MICRON SPATIAL RESOLUTION OF 2.5 X 2.5 CENTIMETER AREAS YIELDING ELEMENTAL CHEMISTRY AT OR BELOW THE SCALE LENGTH WHERE MANY RELICT PHYSICAL CHEMICAL AND BIOLOGICAL FEATURES CAN BE IMAGED AND INTERPRETED IN ANCIENT ROCKS. MAPX IS AN ARM-BASED INSTRUMENT PLACED DIRECTLY ON THE SURFACE OF AN OBJECT TO BE ANALYZED AND HELD IN REGISTRY WITH IT THROUGH THE USE OF TOUCH SENSORS THAT PHYSICALLY CONTACT THE SURFACE. DURING AN ANALYSIS EITHER AN X-RAY TUBE OR A RADIOISOTOPE SOURCE BOMBARDS THE SAMPLE SURFACE WITH X-RAYS (TUBE SOURCE) OR ALPHA-PARTICLES AND GAMMA-RAYS (RADIOISOTOPE SOURCE) RESULTING IN X-RAY FLUORESCENCE FROM THE SAMPLE. FLUORESCED X-RAYS EMITTED IN THE DIRECTION OF AN X-RAY SENSITIVE CCD IMAGER PASS THROUGH AN X-RAY 1:1 FOCUSING LENS (CALLED AN X-RAY MICRO-PORE OPTIC MPO) THAT PROJECTS A SPATIALLY RESOLVED IMAGE OF THE X-RAYS GENERATED FROM THE SAMPLE SURFACE ONTO THE CCD. THE CCD IS READ AT SEVERAL FRAMES PER SECOND SO THAT IN THE MAJORITY OF CASES NO MORE THAN ONE PHOTON STRIKES AN INDIVIDUAL PIXEL BETWEEN READ CYCLES. IN THIS WAY THE ENERGIES AND POSITIONS OF INDIVIDUAL X-RAY PHOTONS ARE RECORDED. THE IMAGES ARE STORED IN MEMORY AND PROCESSED IN REAL TIME USING ALGORITHMS PARAMETERIZED FROM THE GROUND. IN A SINGLE ANALYSIS SEVERAL THOUSAND FRAMES ARE BOTH STORED AND PROCESSED IN REAL-TIME. HIGHER-LEVEL DATA PRODUCTS THAT CAN BE OBTAINED FROM THE RAW IMAGES INCLUDE SINGLE-ELEMENT MAPS FOR ELEMENTS OF INTEREST WITH A LATERAL SPATIAL RESOLUTION OF = 100 MICRONS AND XRF SPECTRA FROM SELECTED REGIONS OF INTEREST (ROI). XRF SPECTRA FROM ROI ARE PROCESSED ON THE GROUND TO DETERMINE QUANTITATIVE ELEMENTAL COMPOSITIONS. QUANTITATIVE COMPOSITIONS FROM ROI ARE COMPARED WITH KNOWN ROCK AND MINERAL COMPOSITIONS TO EXTRAPOLATE THE DATA TO ROCK TYPES AND PUTATIVE MINERALOGIES. A SINGLE MAPX EXPERIMENT PROVIDES ELEMENTAL AND COMPOSITIONAL MAPS AND QUANTITATIVE XRF SPECTRA HAVING A SPATIAL RESOLUTION OF = 100 MICRONS COMMENSURATE WITH OTHER IMAGING INSTRUMENTS. MAPX IS CURRENTLY BEING DEVELOPED UNDER THE PICASSO PROGRAM ( X-RAY MICRO-MAPPING SPECTROMETER 13-PICASSO13-0111) AND WILL BE TRL-4 AT ITS EXIT (04/01/17). THE PROPOSED NEW EFFORT UNDER MATISSE FUNDING IS INTENDED TO INCREASE MAPX S READINESS LEVEL TO TRL-6 SUITABLE FOR PROPOSAL TO FLIGHT OPPORTUNITIES. MAPX SCIENCE OBJECTIVES ARE: (1). TO COLLECT FINE-SCALE ELEMENTAL MAPS OF PLANETARY (E.G. MARS) OR PLANETESIMAL (COMET NUCLEUS ASTEROID PLANETARY SATELLITE (PHOBOS DEIMOS; GALILEAN AND SATURNIAN MOONS; EARTH S MOON)) SURFACE REGOLITH WITH A LATERAL SPATIAL RESOLUTION = 100 MICRONS A LENGTH SCALE COMMENSURATE WITH OTHER IMAGING INSTRUMENTS; AND (2). TO RETURN QUANTITATIVE COMPOSITIONAL INFORMATION (XRF SPECTRA) AND DERIVED MINERALOGICAL INFORMATION FROM REGIONS OF INTEREST (ROI) WITH A SPATIAL RESOLUTION 100 MICRONS<X<2 CENTIMETERS IN IMAGED SURFACE MATERIAL. MAP-X ADDRESSES OBJECTIVE 6 OF THE SOLAR SYSTEM EXPLORATION ROADMAP INCLUDING: UNDERSTANDING THE CURRENT STATE AND EVOLUTION OF THE ATMOSPHERE SURFACE AND INTERIOR OF MARS; INVESTIGATE THE HISTORY AND BEHAVIOR OF WATER AND OTHER VOLATILES ON MARS; STUDY THE CHEMISTRY MINERALOGY AND CHRONOLOGY OF MARTIAN SURFACE MATERIAL; AND INVENTORY AND CHARACTERIZE MARTIAN RESOURCES OF POTENTIAL BENEFIT TO HUMAN EXPLORERS. THIS INVESTIGATION ADDRESSES THE MARS EXPLORATION PROGRAM (MEP) GOAL OF IDENTIFYING AND CHARACTERIZING PAST OR PRESENT HABITABLE ENVIRONMENTS ON MARS USING FINE-SCALE ELEMENTAL CHEMISTRY.